The major objective of this research is to determine whether nonverbal social-communication skills are impaired in young mentally retarded children. The second aim is to determine whether an association exists between levels of nonverbal communication skills and language abilities within samples of normal and retarded children. Finally, the third goal of this research is to address the hypothesis that differences in care-giver behavior are associated with nonverbal social-communication skills in normal and mentally retarded children. In order to identify impairments in the nonverbal social-communication skills of mentally retarded children, developmentally matched samples of normal and mentally retarded children will be observed in structured child-adult interactions designed to measure a well-defined set of nonverbal communication competencies. The generality of nonverbal social-communication impairments related to mental retardation will be assessed by including samples form different diagnostic subgroups of mental retardation and different developmental levels. In order to determine whether an association exists between nonverbal communication skills and language ability the normal and retarded children will be assessed on measures of receptive and expressive language. In addition, observational measures of caregiver-child interaction will be used to test our hypotheses that the caregiver's responsiveness to the child's behavior is an important correlate of early communication skills and that caregivers will be less responsive to young mentally retarded children than to normal children. This examination of social-communication skills will advance our understanding of the development of communicative and social competence in the young mentally retarded child, and it is a first step toward designing interventions aimed at enhancing social and communicative competence in these children.